The potential energy in the DFTB Hamiltonian is generally expressed in one of two forms. In its original formulation[1]}, the Hamiltonian is taken to be a superposition of potentials centered on each atom, which for the purposes of this study we label as the “blackDFTB2-pot” model:
\(\hat{H}^{{AB}}_{{\mu \nu }_{Tr1}} = \left<\phi ^A_\mu | \hat{T} + \hat{V}(n_A) + \hat{V}(n_B) | \phi ^B_\nu \right>\) 
